First, opacity happens when you have another layer selected over another. Second, PSE13 is an old program without support; Third, there has never been a complaint about this and not a fix that I know about and I've been in this forum for a few years;
As an engineer, I cannot think of a work around. Best advice: Get a discount on a newer PSE, maybe 14, 16, 18, and there are older programs still out there selling second hand, some still sealed that came with a scanner and is selling now. Check out the market.
I still use PSE-10 - plus 2, 3, 4, 5, 8, 11, 14, and most of the CS Photoshop's, and Light Room. Be flexible. Improvise. Opacity may be convenience but can be worked with other adjustments also.